The principal goal of this project is to evaluate the ability of ethyl nitrate to attenuate the reduced tissue perfusion and respiratory acidosis produced during carbon dioxide pneumoperitoneum. The studies will use a novel method of drug delivery: inclusion of ethyl nitrate in the insufflating gas. Laparoseopy has rapidly become the method of choice for surgical intervention to correct abdominal pathologies. However, pneumoperiteneum, the act of insufflating the peritoneal cavity with gas, is not without physiologic consequence: pulmonary function is impaired and organ blood flows altered. In addition, due to its plasma solubility, insufflation with CO2 will increase pCOz and decrease blood pH, actions that can produce respiratory acidosis, tachycardia, and arrhythmia. The overall effects can become profound in the presence of underlying vascular disease, in[ the elderly, if the patient is pregnant, and/or when the duration of surgery is extended. In all situations, tissue ischemia and fetal ischemia (where applicable) can produce significant morbidity. To control this, it is a logical supposition that administration of a vasoactive agent to increase tissue blood flow and gas exchange would be beneficial. For the purposes of this study, we propose to introduce a nitric oxide donator (ethyl nitrate; E-NO) into the insufflating gas. As the released nitric oxide can act locally (i.e. within the peritoneum) as well as entering the systemic circulation and, in the case of the gravid patient, the fetal circulation (either by diffusion or maternal-fetal exchange), this would appear to be an ideal methodology to abate the CO2 pnenmoperiteneum-mediated changes in physiologic status. Such abatement is expected to be of long-term benefit to all laparoscopic patients including the parturient and her fetus. To evaluate this novel therapy, we will test two research hypotheses: 1. In the non-gravida, inclusion of E-NO in the insufflating gas attenuates the tissue perfusion changes produced by CO2 pneumoperitoneum; and 2. In the parturient, inclusion of E-NO during maternal pneumoperitoneum stabilizes fetal physiologic status. Studies will utilize adult swine and pregnant sheep. Completion of this investigation will produce clinically-relevant information that will be of significant interest to surgeons With patients in need of laparoscopic surgery and to obstetricians who are presented with parturients in abdominal distress. It is expected that the results of these studies will be used to further develop and refine standards of care for human laparoscopy and will lead to a novel therapy for controlling the blood flow changes produced during pneumoperitoneum.